456 Dandeno — Relation of Mass Action to Toxicity. 



It should be remembered always that the test applied to decide 

 life was further growth in water after the seedling was taken 

 from the test solution. Column 4 gives the number of cc. in 

 which the radicle just lived at the concentration opposite in 

 column 3. In column 6 is given the concentration the seed- 

 lings would endure when sand was present ; the amount of solu- 

 tion to each radicle was 3^ to 6 CC , and the amount of sand about 

 5 to 8 CC . 



A comparison between columns 3 and 5 in Table XX shows 

 the variation due to quantity of solution. (It ought to be 

 mentioned that when the experiments were arranged, the 

 liquid used in all the vials of different size was taken from 

 the same preparation, so that practically every element which 

 might affect results was eliminated.) It may be seen further 

 that a comparison of these results with those of Heald shows 

 some difference of figures. No attempt is here made to recon- 

 cile these differences because a general actual toxic limit is not 

 possible to obtain. 



Column 6 shows clearly that the presence of sand affects the 

 characters of the solution in regard to toxicity. In dilute solu- 

 tions it reduces it enormously ; in strong solutions not nearly 

 so much. Though the figures opposite JSIalICO, are close, yet 

 if working with more closely graded quantities and concentra- 

 tions slightly different results from those given might be 

 expected. 



The problem of soils, examined from this point of view, 

 presents a very complicated question, from the fact that sev- 

 eral substances enter into the composition of soil water. It is 

 then a problem of permutations and combinations of (n + 1) 

 substances, making factorial n cases for each combination. 

 And, since the amount of each may vary from an insignificantly 

 small to a predominating quantity, the number of problems 

 from this side is at once enormous ; and if the theory of dis- 

 sociation be admitted into the proposition, the problem is still 

 more complicated. There is then the possibility of ion effect, 

 coupled with electrical forces, augmented or neutralized by 

 the presence of a number of different ions. 



In order to learn something of the differences in effect 

 between fine and coarse sand, solutions of CuS0 4 , n/8192, HC1, 

 7&/512, H 2 S0 4 ,?i/512 w T ere compared with the following results: 

 more growth was permitted in fine sand with CuS0 4 but, on 

 the other hand, considerably more growth was permitted with 

 coarse sand when HC1 and H 2 S0 4 were used. In all the 

 experiments these were the general results, H 2 S0 4 presenting 

 the most marked character. One explanation of this may be 

 that because of the greater surface, the fine sand would hold 

 mechanically more of the solute when in very dilute solution 



